Here is a real mixture of addition and subtraction questions which can all be answered mentally without resorting to written methods. The questions include adding 2-digit multiples of 10 to 3-digit numbers and subtracting 2-digit multiples of 10 from 3-digit numbers. Interestingly, some of the addition statements can be answered by subtraction and some of the subtraction statements can be completed by addition. For example: 35 + ?? = 75 can be done by subtracting 35 from 75. An equally good method would be to add on in tens from 35 to 75. In the same way 36 - ?? = 20 can be completed by adding on from 20 up to 36, or simply by subtracting 20 from 36. This all helps with understanding the relationship between addition and subtraction. This set of worksheets, which because it involves both addition and subtraction is slightly harder than just dealing with one, can be found in the Year 4 addition category. Go to Year 4 addition and subtraction questions